First, it is not necessarily the word itself so much so as how one feels when he/she hears the word. For example, if one is a professional, well education female, it is not likely that she would want to be called "girl"; yet, the word "girl" is not offensive in and of itself.
"You" is not offensive, nor is "people"; but, put the two together: you people, and that may come across as racist and therefore offensive.
There's probably a list of foul words somewhere, but then, the argument would be "how foul is foul". Just listen to TV today to hear how "foul" words have become common in prime time, where once they were considered not appropriate, yet this not necessarily mean they are now appropriate.
When words offend people, they tend to make the people angry or to make them feel worse about themselves. I believe that the words that offend people most are the ones that reinforce existing fears that people have about themselves, either as individuals or as members of some group.
For example, a person who has always been overweight will fear that people look down on him for being that way. If someone calls him fat, he will be very offended because that is something that actually worries him. Calling a thin person fat will not be offensive.
Similarly, if you use an ethnic stereotype against someone, you can offend them, but only if they worry that people will believe that stereotype is true of them.
Overall, then, the words that hurt or anger people most are words that call attention to something that worries them.